Solder alloy, solder ball, solder preform, solder paste, and solder joint

Abstract

Provided are a solder alloy and a solder joint which have excellent wettability and high reliability by prevention of rupture of solder joints. The solder alloy has an alloy composition consisting of, by mass%, Ag: 1.0 to 3.7%, Cu: 0.4 to 0.8%, Sb: 0.50 to 2.90%, In: 5.00 to 10.00%, and Ni: 0.01 to 0.06%, with the balance being Sn.

Description

Solder alloys, solder balls, solder preforms, solder pastes and solder joints

[0001] The present invention relates to solder alloys, solder balls, solder preforms, solder pastes and solder joints for use in various electronic devices.

[0002] In recent years, the increasing sophistication of consumer electronic devices such as personal computers has dramatically improved the performance of electronic components mounted on circuit boards. As electronic components become more powerful, larger currents are passed through them, which means that solder joints used on circuit boards for consumer electronic devices are sometimes exposed to high temperatures. Furthermore, when a circuit board and an electronic component are joined by step soldering, the solder joints are exposed to high temperatures of around 150°C. Meanwhile, it is easy to imagine that consumer electronic devices will be used in cold climates.

[0003] In addition to consumer electronic components, applications in which solder joints are exposed to harsh environments include automotive electronic devices and industrial electronic devices. Automobiles are increasingly powered by electronics, transitioning from gasoline-powered vehicles to hybrid vehicles and then electric vehicles. As a result, the circuit boards of automotive electronic devices are sometimes placed in locations exposed to high temperatures, such as the engine compartment, due to the expansion of their uses. Meanwhile, when the engine is stopped, they are exposed to temperatures as low as -40°C or below in cold regions. Furthermore, depending on the usage environment, electronic devices may be subjected to physical external forces, such as impacts.

[0004] Furthermore, industrial electronic devices are used in locations where it is difficult for workers to work, and therefore, like boards for automotive electronic devices, industrial electronic device circuit boards are likely to be exposed to environments with large temperature differences and to be subjected to external forces.

[0005] Sn-3Ag-0.5Cu solder alloys are widely used to connect substrates and electronic components. The range of applications for solder alloys is expanding, but this has led to a growing demand for high connection reliability that prevents breakage or deterioration of solder joints even when used for long periods in harsh environments, such as in automotive applications.

[0006] However, when electronic circuits are exposed to the above-mentioned temperature differences, stress concentrates on the solder joints due to the difference in thermal expansion coefficients between the electronic components and the printed circuit board. Furthermore, when external force is applied to the electronic device, stress concentrates on the solder joints with small cross-sectional areas. Therefore, there is a concern that the use of conventional Sn-3Ag-0.5Cu solder alloys may cause the solder joints to fracture, and a solder alloy that can prevent this is needed.

[0007] For example, Patent Document 1 discloses an alloy composition in which an Sn-Ag-Cu-Sb-In solder alloy may contain optional elements such as Ni, as a solder alloy that suppresses lift-off when a fillet is formed in a through-hole of a substrate, has excellent wettability and spreadability of molten solder, and exhibits low crack propagation due to thermal cycling. Comparative Example 6 in the same document discloses a solder alloy containing 3.5 mass% Ag, 0.8 mass% Cu, 1.0 mass% Sb, 6.0 mass% In, 0.07 mass% Ni, and the remainder being Sn.

[0008] Patent Document 2 discloses an alloy composition in which an Sn-Ag-Bi-Ni-Co solder alloy may contain optional elements such as Sb and In, as a solder alloy with a small intermetallic compound structure, excellent crack resistance, suppressed voids and Cu erosion, and excellent durability due to suppressed crack propagation after thermal cycling. Example 40 of this document discloses a solder alloy containing 3.0 mass% Ag, 0.5 mass% Cu, 1.5 mass% Sb, 4.3 mass% In, 0.05 mass% Ni, 0.5 mass% Bi, 0.005 mass% Co, and the remainder being Sn.

[0009] JP 2019-063830 A JP 2014-037005 A

[0010] However, as mentioned above, the solder alloys described in Patent Documents 1 and 2 are designed with a focus primarily on heat cycle characteristics. When electronic devices are exposed to heat cycles, stress is applied to solder joints due to the difference in thermal expansion coefficients between the board and electronic components. On the other hand, when vibrations are applied to in-vehicle electronic circuits, the manner in which the stress is applied is thought to be different from the stress caused by expansion and contraction of printed circuit boards and electronic components that occurs during heat cycles. As such, in order to avoid fracture of solder joints even when various stresses are applied to solder joints due to the deterioration of the usage environment caused by the recent increase in the functionality of electronic devices and the expansion of their applications, it is necessary to improve the strength of the solder alloy itself.

[0011] In addition to the fracture of the solder alloy that constitutes the solder joint, fracture at the joint interface caused by poor wettability of the solder alloy can also be considered. Thus, in order to form solder joints with higher reliability than conventional ones, it is necessary to reconsider the known alloy compositions.

[0012] An object of the present invention is to provide a solder alloy, a solder ball, a solder preform, a solder paste, and a solder joint that have excellent wettability and high reliability due to suppression of fracture of the solder joint.

[0013] The inventors investigated alloy compositions of Sn-Ag-Cu solder alloys that can alleviate various stresses. It was previously believed that solder alloys that undergo large volume changes during thermal cycling would fracture due to the difference in the linear expansion coefficient between the solder alloy and the substrate. However, if the volume change is small, the applied stress accumulates in the solder alloy as strain energy, which may actually accelerate fracture.

[0014] First, we focused on In, which causes a volume change in the solder alloy so as to alleviate the stress applied during heating in a thermal cycle. Indium promotes the solid-state transformation between βSn and γSn depending on the content, causing a volume change due to the solid-state transformation. Therefore, the inventors investigated solder alloys with a high In content, as described in Patent Document 1.

[0015] However, if the volume change is large, the solder joint will fracture at the joint interface. Therefore, the inventors conducted detailed studies on the contents of Cu, Sb, and Ni from the viewpoints of the wettability of the molten solder and the refinement of the alloy structure in the solder alloy and at the joint interface. Furthermore, the inventors also conducted detailed studies on the Ag content, noting that if a solid-phase transformation from βSn to γSn occurs immediately when the temperature of the solder joint rises during a thermal cycle, stress is quickly relieved. As a result, they discovered that a solder alloy in which the contents of the additive elements Ag, Cu, Sb, In, and Ni are all within the specified ranges simultaneously has excellent wettability and suppresses fracture of the solder joint, and thus completed the present invention.

[0016] The present invention, which was made based on these findings, is as follows: (1) A solder alloy characterized by having an alloy composition, in mass %, of 1.0 to 3.7% Ag, 0.4 to 0.8% Cu, 0.50 to 2.90% Sb, 5.00 to 10.00% In, 0.01 to 0.06% Ni, and the balance being Sn.

[0017] (2) The solder alloy according to (1) above, further containing, by mass%, Co: 0.100% or less.

[0018] (3) The solder alloy according to (1) or (2) above, further containing, by mass %, Bi: 5.0% or less.

[0019] (4) The solder alloy according to any one of (1) to (3), further containing, by mass%, 0.1% or less in total of at least one of Zr, Fe, Ge, Ga, P, As, Pb, Zn, Mg, Cr, Ti, Mn, Mo, Pt, Pd, Au, Al, and Si.

[0020] (5) A solder alloy according to any one of (1) to (5) above, wherein the alloy composition satisfies the following formulas (1) and (2): 132≦(In / Sb)×(Sn / Ag)≦450 (1) 251≦In / (Cu×Sb×Ni)≦699 (2) In the formulas (1) and (2), In, Sb, Sn, Ag, Cu, and Ni represent the contents (mass %) of the alloy composition.

[0021] (6) A soldered joint having the solder alloy according to any one of (1) to (5) above.

[0022] (7) A solder preform made of the solder alloy according to any one of (1) to (5) above.

[0023] (8) A solder paste containing solder powder made of the solder alloy according to any one of (1) to (5) above.

[0024] (9) A soldered joint having the solder alloy according to any one of (1) to (5) above.

[0025] 1A and 1B are SEM photographs of the cross sections of the solder alloys, where FIG. 1A is Example 6, FIG. 1B is Comparative Example 3, and FIG. 1C is Comparative Example 8.

[0026] The present invention will be described in more detail below. In this specification, "%" relating to the solder alloy composition is "% by mass" unless otherwise specified.

[0027] 1. Solder Alloy (1) Ag: 1.0 to 3.7% Ag lowers the temperature at which βSn transforms into γSn, thereby quickly alleviating strain energy during temperature rise and preventing fracture of the solder joint. ３ The Ag content of less than 1.0% results in a low temperature of the phase transformation from βSn to γSn, which prevents the phase transformation from occurring and prevents the fracture of the solder joint. ３ The lower limit of the Ag content is 1.0% or more, preferably 1.5% or more, and more preferably 2.0% or more. On the other hand, if the Ag content exceeds 3.7%, coarse Ag particles are formed. ３ Primary crystals of Sn are crystallized, which deteriorates the strength.The upper limit of the Ag content is 3.7% or less, preferably 3.0% or less, and more preferably 2.3% or less.

[0028] (2) Cu: 0.4-0.8% Cu can improve the wettability of molten solder by suppressing the liquidus temperature. If the Cu content is less than 0.4% or more than 0.8%, the liquidus temperature rises, reducing fluidity at the joining temperature and deteriorating wettability. Furthermore, if the Cu content exceeds 0.8%, compounds with Sn precipitate, hardening the intermetallic compounds formed at the joining interface. The lower limit of the Cu content is 0.4% or more, preferably 0.5% or more. The upper limit of the Cu content is 0.8% or less, preferably 0.7% or less, and more preferably 0.6% or less.

[0029] (3) Sb: 0.50 to 2.90% When Sb is added to a solder alloy containing a specified amount of In, it crystallizes fine InSb compounds, improving the strength of the solder alloy itself. Furthermore, the solid solubility limit of Sb in Sn varies over the operating temperature range, including room temperature, so Sb repeatedly dissolves in Sn and precipitates as the temperature changes. Furthermore, Sb forms a supersaturated solid solution at high temperatures, improving the bulk strength of the solder alloy through solid solution strengthening. This lowers the liquidus temperature, improving wettability.

[0030] If the Sb content is less than 0.50%, the bulk strength cannot be improved by solid solution strengthening and dispersed precipitation strengthening. Furthermore, the InSb compound does not become fine, and the bulk strength does not improve. The lower limit of the Sb content is 0.50% or more, preferably 0.70% or more, and more preferably 1.00% or more. On the other hand, if the Sb content exceeds 2.90%, the crystallization of coarse InSb compounds causes the sustainability of dispersed precipitation strengthening to disappear. The upper limit of the Sb content is 2.90% or less, preferably 2.50% or less, and more preferably 2.30% or less.

[0031] (4) In: 5.00 to 10.00%. When the transformation point is reached by temperature change, In gradually transforms βSn to γSn, thereby alleviating strain energy and preventing solder joint fracture. Conventionally, it has been thought that solder joints are more susceptible to fracture when the volume change during thermal cycling is large. However, in the present invention, the alloy composition is deliberately adjusted to increase the volume change, thereby preventing solder joint fracture more effectively than conventional solder alloys. If the In content is less than 5.0%, the solid-state transformation of the Sn phase does not occur. The lower limit of the In content is 5.0% or more, preferably 6.00% or more, and more preferably 7.50% or more. On the other hand, if the In content exceeds 10.00%, the liquidus temperature drops too much, and the solid-state transformation of the Sn phase does not occur. The upper limit of the In content is 10.00% or less, preferably 9.00% or less.

[0032] (5) Ni: 0.01 to 0.06% Ni inhibits the diffusion of Cu into Sn after soldering, suppresses the growth of intermetallic compounds precipitated at the joint interface, and suppresses the coarsening of metallic compounds precipitated at the joint interface, thereby strengthening the joint interface. If the Ni content is less than 0.01%, the joint interface cannot be strengthened. The lower limit of the Ni content is 0.01% or more, preferably 0.02% or more, and more preferably 0.03% or more. On the other hand, if the Ni content exceeds 0.06%, the liquidus temperature increases, resulting in a decrease in wettability. The upper limit of the Ni content is 0.06% or less, preferably 0.05% or less, and more preferably 0.04% or less.

[0033] (6) Balance: Sn The balance of the solder alloy according to the present invention is Sn. In addition to the above elements, unavoidable impurities may be contained. Even if unavoidable impurities are contained, the above-mentioned effects are not affected.

[0034] (7) Co: 0.100% or less Co is an optional element that has the effect of suppressing the growth of intermetallic compounds and refining the alloy structure. The upper limit of the Co content is preferably 0.100% or less, more preferably 0.050% or less, and even more preferably 0.010% or less. The lower limit of the Co content is not particularly limited, but from the viewpoint of refining the alloy structure, it is preferably 0.001% or more, more preferably 0.003% or more, even more preferably 0.005% or more, still more preferably 0.006% or more, particularly preferably 0.007% or more, and most preferably 0.008% or more.

[0035] (8) Bi: 5.0% or less Bi is an optional element that dissolves in the Sn phase and can improve the strength of the solder alloy. Furthermore, when an appropriate amount of Bi is added, the solder alloy does not become embrittled and may maintain high strength. The upper limit of the Bi content is preferably 5.0% or less, more preferably 1.0% or less, and even more preferably 0.3% or less. The lower limit of the Bi content is not particularly limited, but from the viewpoint of sufficient solid solution strengthening, it is sufficient if it is 0.1% or more.

[0036] (9) Other Optional Elements In addition to the above, the solder alloy according to the present invention may contain at least one of Zr, Fe, Ge, Ga, P, As, Pb, Zn, Mg, Cr, Ti, Mn, Mo, Pt, Pd, Au, Al, and Si in a total amount of 0.1% or less. Even if these elements are contained in an amount of 0.1% or less, coarse compounds are not precipitated, and the above-mentioned effects of the present invention can be achieved. The total content of these elements is preferably 0.1% or less, more preferably 0.09% or less, and even more preferably 0.05% or less. The content of each element is not particularly limited, but is preferably 0.0003 to 0.02%. Among these, Fe, like Ni, inhibits the diffusion of Cu into Sn after soldering, suppresses the growth of intermetallic compounds precipitated at the joint interface, and also suppresses the coarsening of metallic compounds precipitated at the joint interface, thereby strengthening the joint interface.

[0037] (10) Equations (1) and (2): 132≦(In / Sb)×(Sn / Ag)≦450 (1) 251≦In / (Cu×Sb×Ni)≦699 (2) In the above equations (1) and (2), In, Sb, Sn, Ag, Cu, and Ni represent the contents (mass%) of the alloy composition. It is preferable that the solder alloy according to the present invention satisfies equations (1) and (2). When both equations are satisfied, the strength of the solder alloy itself is improved, and wettability can be improved by optimizing the liquidus temperature.

[0038] When the solder alloy of the present invention satisfies the formula (1), Ag ３ The dense crystallization of Sn and the fine crystallization of InSb synergistically further improve bulk strength. In order for each intermetallic compound to be dense and finely crystallized, it is desirable that the constituent elements of each intermetallic compound are contained in a balanced manner. Furthermore, it is presumed that coarsening of the intermetallic compounds is suppressed by dispersing the crystallized amounts of the intermetallic compounds without bias toward either one. The lower limit of formula (1) is preferably 132 or more, more preferably 150 or more, and particularly preferably 180 or more. The upper limit of formula (1) is preferably 450 or less, more preferably 430 or less, and even more preferably 410 or less.

[0039] Furthermore, when the solder alloy of the present invention satisfies formula (2), the liquidus temperature can be adjusted to a more appropriate range. To achieve this, it is desirable to maintain a balance between In, whose liquidus temperature decreases when its content is high, and Cu, Sb, and Ni, whose liquidus temperature increases when its content is high. In particular, Cu, Sb, and Ni form intermetallic compounds with higher melting points than Sn, so in order to optimize the liquidus temperature, it is desirable to adjust their contents together with the In content. The lower limit of formula (2) is preferably 251 or more, more preferably 300 or more, and particularly preferably 345 or more. The upper limit of formula (2) is preferably 699 or less, more preferably 600 or less, and even more preferably 500 or less.

[0040] As described above, the solder alloy according to the present invention contains Ag in order to improve the mechanical properties.３ It is desirable that Sn is densely crystallized and InSb is finely crystallized. The evaluation of density and fineness is generally based on the average crystal grain size. However, if even one coarse compound is present, the mechanical properties of the solder alloy may be deteriorated. Therefore, in the present invention, attention is paid to the maximum crystal grain size of these compounds, and if the maximum crystal grain size is small, it can be evaluated as having a dense and fine structure. Ag ３ For Sn, the grain size is preferably an optimum size for forming a network, and the maximum crystal grain size is preferably 5 to 15 μm, more preferably 5 to 10 μm, and may be more than 10 μm but not more than 15 μm.For InSb, the maximum crystal grain size is preferably 7 μm or less, more preferably 5 μm or less, and even more preferably 1.8 μm or less.

[0041] 2. Solder Balls The solder alloy according to the present invention can be used as solder balls. The solder balls according to the present invention are used to form electrodes of semiconductor packages such as BGA (ball grid array) and bumps on substrates. The diameter of the solder balls according to the present invention is preferably within the range of 1 to 1000 μm. The solder balls can be manufactured by a general solder ball manufacturing method.

[0042] 3. Solder Preform The shape of the solder preform according to the present invention is not particularly limited, and it can be used in shapes such as a plate, ring, cylinder, ribbon, square, disk, washer, chip, wire, etc. The solder preform may contain high-melting-point metal particles (e.g., Ni particles or Cu particles, and alloy powder mainly composed of Ni or Cu) therein, which have a higher melting point than the solder alloy and are easily wetted by molten solder.

[0043] 4. Solder Paste The solder alloy according to the present invention can be used as a solder paste. A solder paste is prepared by mixing a solder alloy powder with a small amount of flux to form a paste. The solder alloy according to the present invention may be used as a solder paste for mounting electronic components on a printed circuit board by reflow soldering. The flux used in the solder paste may be either a water-soluble flux or a water-insoluble flux. Typically, a rosin-based flux, which is a water-insoluble flux based on rosin, is used.

[0044] 5. Solder Joint The solder joint according to the present invention connects an IC chip and its substrate (interposer) in a semiconductor package, or joins and connects a semiconductor package and a printed circuit board. In other words, the solder joint according to the present invention refers to the connection portion of electrodes, and can be formed using general soldering conditions.

[0045] The bonding method using the solder alloy of the present invention may be carried out in accordance with a conventional method, such as step soldering by a reflow method. The heating temperature may be adjusted appropriately depending on the heat resistance of the chip and the liquidus temperature of the solder alloy. Other bonding conditions may be adjusted appropriately depending on the alloy composition of the solder alloy.

[0046] Solder alloys having the alloy compositions shown in Tables 1 and 2 were prepared, and the liquidus temperatures were measured as Evaluation 1. ３ The density of Sn was evaluated, the refinement of InSb was evaluated as evaluation 3, the solid phase transformation of Sn phase was evaluated as evaluation 4, and the uniform refinement of the bonding interface was evaluated as evaluation 5.

[0047] Evaluation 1: Liquidus temperature Each solder alloy in Table 1 was prepared, and the liquidus temperature of the solder alloy was measured. The liquidus temperature was measured using a DSC method similar to the method for measuring solidus temperature in JIS Z 3198-1. Liquidus temperatures between 200 and 215°C were evaluated as "Good", temperatures above 215°C were evaluated as "Poor", and temperatures below 200°C were also evaluated as "Poor".

[0048] Ratings 2 and 3: Ag ３The solder alloy having the alloy composition shown in Table 1 was cast into a predetermined mold, and the obtained solder alloy was molded with resin and polished. The part where the solder alloy was polished to about half was photographed with FE-SEM at 1000x magnification. Cross-sectional observation and mapping composition analysis by EDS revealed that Ag ３ The density of Sn and the refinement of InSb were evaluated. Each compound was identified by mapping composition analysis, and the largest crystal grain was visually selected. Two parallel tangent lines were drawn to the crystal grain so that the distance between them was maximized, and the distance between them was taken as the maximum crystal grain size. ３ When the maximum crystal grain size of Sn was 5 μm or more and 10 μm or less, it was marked with "◎", when it was more than 10 μm and 15 μm or less, it was marked with "◯", when it was less than 5 μm or more than 15 μm, it was marked with "X". When the maximum crystal grain size of InSb was 1.8 μm or less, it was marked with "◎", when it was more than 1.8 μm and 7 μm or less, it was marked with "◯", and when it was more than 7 μm, it was marked with "X".

[0049] Evaluation 4: Solid-state transformation of Sn phase Solder balls with a diameter of 0.6 mm were prepared from each solder alloy listed in Table 1. These solder balls were subjected to 200 cycles of heat cycles between -40°C and 125°C using a thermostatic chamber, and evaluation was performed under an environment in which solid-state transformation of the Sn phase occurred. The solder balls were then removed from the thermostatic chamber and evaluated for sphericity. The sphericity was measured using a CNC image measuring system. The equipment used was the Ultra Quick Vision ULTRA QV350-PRO manufactured by Mitutoyo Corporation. Sphericity less than 0.95 was evaluated as "◎", sphericity between 0.95 and 0.99 was evaluated as "◯", and sphericity of 0.99 or greater was evaluated as "X".

[0050] Evaluation 5: Uniform refinement of the bonding interface. A 0.6 mm diameter solder ball was prepared from each solder alloy listed in Table 1 and mounted on a Cu pad. The solder ball was then reflowed at 245°C to produce a solder bump. The uniform refinement of the bonding interface was evaluated by measuring the thickness of the intermetallic compound (IMC) from a cross-sectional SEM photograph of the cross section of the bonding interface between the solder bump and the Cu pad. Since the intermetallic compound layer becomes thinner when the bonding interface is uniform and refined, in Evaluation 5, the uniform refinement was evaluated by the thickness of the intermetallic compound. The cross-sectional SEM photograph was analyzed using image analysis software (Scandium, manufactured by Seika Sangyo Co., Ltd.) to measure the thickness of the intermetallic compound layer. If the thickness of the intermetallic compound was 1.5 μm or less, it was evaluated as "◎", if it was more than 1.5 μm and less than 2.5 μm, it was evaluated as "◯", and if it was more than 2.5 μm, it was evaluated as "×". The evaluation results are shown in Tables 1 to 3.

[0051]

[0052]

[0053]

[0054] As is clear from Tables 1 to 3, in Examples 1 to 48, all of the constituent elements were appropriate, and therefore the liquidus temperatures were within the predetermined range. ３ The Sn was dense, the InSb was fine, a solid phase transformation from βSn to γSn was confirmed, and the structure of the bonding interface was uniform and fine. In particular, Examples 3 to 8, 14, 15, and 18 to 48, which satisfied the formulas (1) and (2), were confirmed to show excellent results in all evaluations.

[0055] On the other hand, in Comparative Example 1, the Ag content is low and In is not contained, so Ag is not added to the extent that the bulk strength is improved. ３ In Comparative Examples 2 and 3, the Ag content was not appropriate, and therefore the Ag content was not sufficient to improve the bulk strength. ３ The Sn did not become dense.

[0056] In Comparative Examples 4 to 6, the Cu content was inappropriate, so the liquidus temperature did not reach a temperature at which excellent wettability was exhibited.In Comparative Examples 7 and 8, the Sb content was inappropriate, so the InSb was not fine enough to improve the bulk strength.

[0057] In Comparative Examples 9 to 11, the In content was inappropriate, so solid-state transformation of the Sn phase could not be confirmed. Furthermore, in Comparative Example 11, Sb was not contained, so InSb compounds were not precipitated. In Comparative Examples 12 and 13, the Ni content was low, so uniform refinement of the bonding interface could not be confirmed. Furthermore, in Comparative Example 12, Sb was not contained, so InSb compounds were not precipitated. In Comparative Example 14, the Ni content was high, so the liquidus temperature showing excellent wettability was not reached.

[0058] These results will be explained using the figures. Figure 1 shows cross-sectional SEM photographs of the solder alloys, where Figure 1(a) is Example 6, Figure 1(b) is Comparative Example 3, and Figure 1(c) is Comparative Example 8. The Ag ３ As is clear from FIG. 1, in Example 6, the grain size of Ag was measured. ３ It was found that Sn was 10 μm or less and densely crystallized, and InSb was finely crystallized. It was also found that the intermetallic compounds precipitated at the bonding interface were uniform and fine, resulting in a thin film. On the other hand, in Comparative Example 3, Ag ３ It was found that Sn was coarse. In Comparative Example 8, it was found that InSb was coarse.

Claims

1. A solder alloy characterized by having an alloy composition consisting, in mass%, of 1.0 to 3.7% Ag, 0.4 to 0.8% Cu, 0.50 to 2.90% Sb, 5.00 to 10.00% In, 0.01 to 0.06% Ni, and the balance being Sn.

2. The solder alloy according to claim 1, further containing, by mass%, Co: 0.100% or less.

3. The solder alloy according to claim 1 or 2, further containing, by mass%, Bi: 1.0% or less.

4. The solder alloy according to claim 1 or 2, further containing, by mass%, 0.1% or less in total of at least one of Zr, Fe, Ge, Ga, P, As, Pb, Zn, Mg, Cr, Ti, Mn, Mo, Pt, Pd, Au, Al, and Si.

5. The solder alloy according to claim 1 or 2, further containing, by mass%, 5.0% or less of Bi, and 0.1% or less in total of at least one of Zr, Ge, Ga, As, Pb, Mg, Cr, Ti, Mn, Mo, Pt, Pd, and Si.

6. The solder alloy according to any one of claims 1 to 5, wherein the alloy composition satisfies the following formulas (1) and (2): 132≦(In / Sb)×(Sn / Ag)≦450 (1) 251≦In / (Cu×Sb×Ni)≦699 (2) In the formulas (1) and (2), In, Sb, Sn, Ag, Cu, and Ni represent the content (mass %) of the alloy composition.

7. A solder ball made of the solder alloy according to any one of claims 1 to 6.

8. A solder preform made of the solder alloy according to any one of claims 1 to 6.

9. A solder paste comprising a solder powder made of the solder alloy according to any one of claims 1 to 6.

10. A solder joint comprising the solder alloy according to any one of claims 1 to 6.